support launch index specific user-data

EC2 and openstack provide 'launch_index' in their metadata. This allows
the user to specify cloud-config or multipart mime data that includes the
'Launch-Index' header.

If launch index is available in the metadata service, then:
 * any part that contains a launch index other than the current launch-index
   of this instance will be ignored.
 * any part that does not contain a launch index will be considered as
   for this instance.

If there is no such header, or launch_index is not available in the metadata
service, then no such filtering will be done.

LP: #1023177

2 files changed, 96 insertions, 0 deletions

diff --git a/cloudinit/filters/__init__.py b/cloudinit/filters/__init__.py
new file mode 100644
index 00000000..da124641
--- /dev/null
+++ b/cloudinit/filters/__init__.py
@@ -0,0 +1,21 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Canonical Ltd.
+#    Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Scott Moser <scott.moser@canonical.com>
+#    Author: Juerg Haefliger <juerg.haefliger@hp.com>
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
diff --git a/cloudinit/filters/launch_index.py b/cloudinit/filters/launch_index.py
new file mode 100644
index 00000000..4299fb46
--- /dev/null
+++ b/cloudinit/filters/launch_index.py
@@ -0,0 +1,75 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Canonical Ltd.
+#    Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Scott Moser <scott.moser@canonical.com>
+#    Author: Juerg Haefliger <juerg.haefliger@hp.com>
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import copy
+
+from cloudinit import log as logging
+from cloudinit import user_data as ud
+from cloudinit import util
+
+LOG = logging.getLogger(__name__)
+
+
+class Filter(object):
+    def __init__(self, wanted_idx, allow_none=True):
+        self.wanted_idx = wanted_idx
+        self.allow_none = allow_none
+
+    def _select(self, message):
+        msg_idx = message.get('Launch-Index', None)
+        if self.allow_none and msg_idx is None:
+            return True
+        msg_idx = util.safe_int(msg_idx)
+        if msg_idx != self.wanted_idx:
+            return False
+        return True
+
+    def _do_filter(self, message):
+        # Don't use walk() here since we want to do the reforming of the 
+        # messages ourselves and not flatten the message listings...
+        if not self._select(message):
+            return None
+        if message.is_multipart():
+            # Recreate it and its child messages
+            prev_msgs = message.get_payload(decode=False)
+            new_msgs = []
+            discarded = 0
+            for m in prev_msgs:
+                m = self._do_filter(m)
+                if m is not None:
+                    new_msgs.append(m)
+                else:
+                    discarded += 1
+            LOG.debug(("Discarding %s multipart messages "
+                       "which do not match launch index %s"),
+                       discarded, self.wanted_idx)
+            new_message = copy.copy(message)
+            new_message.set_payload(new_msgs)
+            new_message[ud.ATTACHMENT_FIELD] = str(len(new_msgs))
+            return new_message
+        else:
+            return copy.copy(message)
+
+    def apply(self, root_message):
+        if self.wanted_idx is None:
+            return root_message
+        return self._do_filter(root_message)